This invention relates to an electron beam device capable of high-resolution survey, or observation, of a semiconductor wafer under low acceleration conditions.
In the field of development and production of semiconductors, improved scanning electron microscopes (SEM) have been demanded which can survey the line width and the like of a pattern provided on a large-size wafer using a low accelerating voltage with high resolution.
In view of such circumstances, a conventional SEM uses an objective lens as shown in FIG. 2 (see The 132nd Committee of Application of Charged Particle Beam to Industry, 1989, page 159). This SEM can survey and measure a large-size semiconductor wafer using an accelerating voltage of 1 KV with a resolution of as fine as 8 nm.
However, such a degree of resolution as above is not sufficient nowadays because the degree of integration of super LSI circuitry has been increased to significantly decrease the line width and the like of a pattern.
Referring to FIG. 2, it would be proposed to enhance the resolving power by positioning a sample closer to the objective lens and increasing the magnetomotive force of the lens to decrease the aberration coefficient of the lens. However, since the top face of an inner cylinder is retracted from the end face of an outer cylinder toward an electron beam source, a large-size sample can hardly be positioned closer to the inner cylinder of the objective lens, and since the top face of the inner cylinder is not miniaturized, the focusing magnetomotive force of the lens increases as the sample is caused to approach the inner cylinder; consequently, the conclusion is that the resolving power can hardly be enhanced by the foregoing provision.
Under the prediction that the degree of integration of super LSI circuitry will increase, it is desirable to make it possible to survey and measure a large-size wafer using a low accelerating voltage with higher resolution.